1. Field of the Invention
The present invention relates to an image reading device that scans and reads a document, used in a digital copier, an image scanner, and the like, and an image forming apparatus including the image reading device. In particular, the present invention relates to a sheet-through type image reading device that conveys a document and reads an image.
2. Description of Related Art
Conventionally, there is an image reading device mounted on a multifunction peripheral or the like employing an electrophotographic process, which includes a document conveying device (automatic document feeder) that sequentially feeds sheet-shaped documents to a document placing table (image reading portion) so as to read the documents and discharges the documents from the document placing table after finishing reading the documents. In such an image reading device, two kinds of reading systems may be employed: a sheet-through system in which a document is automatically conveyed by the document conveying device and read with a document holder closed; and a document fixing system in which a document holder is opened/closed for each reading so as to replace a document on the document placing table (contact glass) one by one, and an optical system (scanning means) is moved to read the document. According to the sheet-through system, a reading operation of a document is performed while the optical system in the image reading device is held at a predetermined image reading position without being moved for scanning. On the other hand, according to the document fixing system, the optical system thereof is moved for scanning to thereby perform a reading operation.
In the image reading device employing the sheet-through system described above, when a document is conveyed obliquely with respect to an image reading position, an image to be read is also tilted. In view of this, various methods of adjusting the tilt of the document conveying direction of the document conveying device with respect to the image reading device body have been proposed. For example, there is known an image reading device, in which the document conveying device is connected to the image reading device so as to be displaceable at a first attachment portion that connects the document conveying device to the image reading device while the document conveying device is connected to the image reading device as to be rotatable at a second attachment portion, and fixing means for fixing the document conveying device to a position where the displacement is performed at the first attachment portion is provided.
Further, there is known a document processing device, in which an adjustment bolt for adjusting the tilt of a document conveying device is provided at one place of two hinge portions supporting the document conveying device, and an operation head of the adjustment bolt is placed on a front side of the hinge portion. Further, there is known an image processing device, in which a stay that may be freely opened/closed is provided on a document reading portion, a conveying unit is attached rotatably on the stay, and a positioning mechanism is provided at a rotation end portion of the conveying unit so as to adjust the tilt of the conveying unit with respect to the stay.
However, according to the method in which the document conveying device is connected to the image reading device so as to be displaceable at the first attachment portion while the document conveying device is connected so as to be rotatable with respect to the image reading device at the second attachment portion, and the document conveying device is fixed at the position where the displacement is performed at the first attachment portion, it is necessary to first loosen a screw for fixing a hinge portion to adjust the tilt of the document conveying device with respect to the image reading device, and then fasten the screw, which requires time for adjustment and a tool such as a driver.
On the other hand, according to the method in which an adjustment bolt for adjusting the tilt of the document conveying device is provided, a manual operation is enabled by knurling an operation head of the adjustment bolt. However, in order to fix the position after adjustment, it is necessary to fasten a loose preventing nut, and thus, the position adjustment operation is far from easy. Further, according to the method in which a stay that may be opened/closed freely is provided on the document reading portion while the conveying unit is attached rotatably on the stay, and a positioning mechanism is provided at the rotation end portion of the conveying unit to adjust the tilt of the conveying unit with respect to the stay, a method of fixing the position of the conveying unit after adjustment is unknown. Further, the stay is interposed between the conveying unit and the document reading portion, and hence there is a problem that a parts count and the number of assembly steps increase.